RE: gyro on a plane
Some use it on the ailerons for flying in heavy winds to keep the plane level kind of a self righting thing. Oh and they are going for $75shipped on the heli websites. But if you dont know how to set one up properly it will do more damage to you than good. I use the cheaper futaba gy240's on my heli's they are simpler but I can see little advantage of using one on a plane the tail on a plane doesn't have any huge counter rotation forces to deal with like the other guy said you are better off just learning to fly the plane or maybe feed in some expo or half rates depending on the problem.